The focus of this project is three-fold: (l) to characterize uptake and intracellular processing of unmodified and modified oligonucleotides; (2) to utilize antisense and antigene technology in several in vitro model systems to identify critical events in cell proliferation/viral replication; and (3) to study the efficacy of antisense and antigene reagents as in vivo modulators of gene expression. (l) We have characterized the uptake of modified oligos as an energy-dependent, endocytic process, mediated by at least one cell surface-binding protein. We have devised a novel technique to study olig uptake, intrcellular localization, and association with protein and nucleic acids. This non- invasive technique will permit subcellular localization over time of an internalized oligo. (2) We have confirmed that c-myc inhibition is cytostatic for normal and malignant lymphoid cells and sane Burkitt lymphoma cells can be specifically growth-arrested in vitro with a novel c-myc antisense. We have confirmed that N-myc inhibition leads to reduction in growth secondary to alteration in differentiative status of neuroectoderm-derived cell lines. (3) We have demonstrated that c-myc antisense is particularly effective against several solid tumors, including human and rat glioblastana. In solid tumors, the c-myc antisense oligonucleotide has, in addition to its antisense effects, a sequence-specific, non-antisense mediated, effect on cellular attachment to extracellular matrix.